Budgerigars are small parrots that, like songbirds, have a complex, learned vocal repertoire. Previous findings in the Dooling lab have indicated that budgerigars, like humans, exhibit the Lombard effect - altering the intensity of their vocalizations in response to an increase in ambient noise level (Manabe et al., 1998). Pilot work that I have completed extends these findings in the frequency domain and suggests that budgerigars may only be able to alter the pitch of their vocalizations by a few hundred Hz or less. Here I propose to explore the potential mechanisms underlying vocal production in budgerigars using operant conditioning methods. Specifically, I will examine the typical range of acoustic variation (especially in the frequency, duration, and amplitude domains) measured in the contact calls of these birds and whether these birds can alter the various acoustic parameters of their calls. I am especially interested in determining the limits of acoustic change in contact call production. Results of these studies will contribute greatly to our understanding of the mechanisms underlying vocal production in this species and also offer insights into vocal behavior generally through comparisons with both songbirds and humans. [unreadable] [unreadable]